## Syntax

``Y = dyaddown(X)``
``Y = dyaddown(X,EVENODD)``
``Y = dyaddown(___,'type')``

## Description

````Y = dyaddown(X)` downsamples even-indexed elements of `X`. `Y` contains even-index samples of `X` in this case. Specify `X` as a vector or matrix. When you specify `X` as a vector, the function returns a version of `X` downsampled by 2. ```

example

````Y = dyaddown(X,EVENODD)` downsamples even- or odd-indexed elements of `X`. `Y` can contain even- or odd-indexed samples of `X` depends on the value of `EVENODD`. Specify `X` as a vector. When you specify `X` as a vector, the function returns a version of `X` downsampled by 2. ```
````Y = dyaddown(___,'type')` returns a version of `X` obtained by suppressing columns or rows, or rows and columns of `X` using `'type'` argument. Specify `X` as a matrix.```

## Examples

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Create a vector of data that you want to downsample.

`X1 = 1:10 `
```X1 = 1×10 1 2 3 4 5 6 7 8 9 10 ```

Downsample elements with even indices.

`dse = dyaddown(X1) `
```dse = 1×5 2 4 6 8 10 ```

You can also downsample the elements in X1 by setting `EVENODD` to `0`.

`dse2 = dyaddown(X1,0)`
```dse2 = 1×5 2 4 6 8 10 ```

Downsample elements with odd indices.

`dso = dyaddown(X1,1) `
```dso = 1×5 1 3 5 7 9 ```

Create a matrix data that you want to downsample.

`X = (1:3)'*(1:4)`
```X = 3×4 1 2 3 4 2 4 6 8 3 6 9 12 ```

Downsample columns with even indices.

`dec = dyaddown(X,0,'c') `
```dec = 3×2 2 4 4 8 6 12 ```

Downsample rows with odd indices.

`der = dyaddown(X,1,'r') `
```der = 2×4 1 2 3 4 3 6 9 12 ```

Downsample rows and columns with odd indices.

`dem = dyaddown(X,1,'m') `
```dem = 2×2 1 3 3 9 ```

## Input Arguments

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Data to be downsampled, specified as a vector or matrix. `X` is a vector when you do not use the `'type'` argument in the `dyaddown` function and `X` is a matrix when you use the `'type'` argument in the `dyaddown` function.

Even- or odd-indexed elements of `X`, specified as a positive integer.

`Y` contains the even- or odd-indexed samples of `X` depending on the value of `EVENODD`:

• If `EVENODD` is even, then ```Y(k) = X(2k)```.

• If `EVENODD` is odd, then ```Y(k) = X(2k+1)```.

Example: `dyaddown(X,0)` consists of even-indexed samples.

Type of downsampling , specified as one of the following:

• `'c'` to downsample columns of `X`

• `'r'` to downsample rows of `X`

• `'m'` to downsample rows and columns of `X`

## Output Arguments

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Dyadic downsampled version of `X`, returned as a vector or a matrix.

 Strang, Gilbert, and Truong Nguyen. Wavelets and Filter Banks. Rev. ed. Wellesley, Mass: Wellesley-Cambridge Press, 1997.